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تکرار جستجوی کلیدواژه sequential gaussian simulation در نشریات گروه علوم پایه
sequential gaussian simulation
در نشریات گروه زمین شناسی
تکرار جستجوی کلیدواژه sequential gaussian simulation در مقالات مجلات علمی
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The Gohar-Zamin mine is located in the southwest of Sirjan city in Kerman province, Iran. Geology condition showed that two fault categories played an important role in the formation of crushed and weathered regions in the southern part of the pit. The spatial analysis of the Lugeon variable indicated that the hydraulic conductivity in the rock mass is very low and the groundwater flow is concentrated only in a limited number of high-transmission main gaps. The mine needs to the designing a proper system for dewatering. Hence, a Gaussian simulation method was used to determine the suitable location of the dewatering wells in the vicinity of the pit. Exploratory spatial data analysis (ESDA) was used to examine location maps, histograms, correlations, and variogram of the Lugeon and RQD data. The relationship between Lugeon and RQD with depth demonstrated that the minimum of RQD and maximum of Lugeon were concentrated in certain elevations. The calculated variograms of RQD and Lugeon showed good spatial continuity. Variograms of the normalized values were performed to carry out the Gaussian simulation of the RQD and Lugeonn variables. Probability and uncertainty maps of RQD and Lugeon indicated that the south-eastern parts of the pit play an important role in permeability.Keywords: Permeability, Geostatistics, Lugeon, RQD, sequential Gaussian simulation
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برای بهینه سازی تصمیمات حفاری و برنامه ریزی محل چاه ها در مناطق فشار بالا، تخمین فشار منفذی بسیار ضروری می باشد. به عبارت دیگر در مراحل مختلف مهندسی نفت، پیش بینی قابل اعتماد فشار منفذی، قبل از حفاری بسیار مهم می باشد. پیش بینی فشار منفذی، جهت انتخاب مناسب لوله جداری و وزن گل حفاری بسیار مهم می باشد. هدف اصلی این مطالعه تخمین فشار منفذی به روش های ایتون و باورز و مقایسه دقت و کارایی آنها می باشد. جهت دستیابی به این هدف، در روش باورز، محقیقین جهت ارتباط مستقیم بین سرعت و تنش موثر تلاش کردند. یکی از این مدل ها توسط باورز گسترش داده شد. داده های سرعت و چگالی موجود در محل چاه ها با استفاده از تکنیک ترکیبی شبیه سازی گوسی پی در پی و کوکریجینگ هم مختصات، در فواصل بین چاه ها پراکنده شد. سپس با استفاده از رابطه بین سرعت و تنش موثر، مکعب تنش موثر و رابطه بین چگالی و فشار روباره، مکعب فشار روباره تولید می شود. در نتیجه فشار منفذی سازند با توجه به رابطه ترزاقی تخمین زده می شود. در روش دیگر )ایتون( فشار منفذی با استفاده از اطلاعات چاه نگاری با به کار بردن روش پیش بینی ایتون با اصلاحات مورد نظر در محل چاه ها تخمین زده می شود. در این روش، خط روند زمان گذر صوتی با استفاده از روش ژانگ و با توجه به لیتولوژی تقسیم بندی می شود. نتایج این مطالعه، نشان می دهد که فشار منفذی تخمین زده شده به وسیله روش اصلاح شده ایتون با ضریب نمایی 0. 4 بیشترین شباهت را با داده های فشار اندازه گیری شده دارند.کلید واژگان: فشار منفذی، روش ایتون، روش باورز، مقاومت صوتی، شبیه سازی گوسی پی درپی، کوکریجینگ هم مختصاتSummary: Pore pressure is defined as the pressure of the fluid inside the pore space of the formation that is also known as the formation pressure. When the pore pressure is higher than hydrostatic pressure, it is referred to as overpressure. Knowledge of this pressure is essential for cost-effective drilling, safe well planning, and efficient reservoir modeling. To optimize drilling decisions and well planning in overpressure areas, it is essential to predict pore pressure in the first step. Before drilling, reliable prediction of pore pressure is critically important at different stages of petroleum engineering investigations. Pore pressure prediction has an important application in proper selection of casing and reliable mud weight. Currently pore pressure prediction in carbonate reservoir is still far from satisfaction, and there is no specific method widely accepted. The existing methods and theories in the pore pressure prediction community are almost all based on the shale properties. Although these methods are not the proper way to predict pore pressure in carbonates and may probably lead to dangerous errors, they are still used in the field practice of carbonate reservoirs. Introduction: The generation of abnormal pore pressure in carbonate formation is different from a reservoir to another reservoir because of different depositional and geological conditions. Although most studies currently point out that under-compaction mechanism is the dominant mechanism of abnormal pore pressure generation, the role of this mechanism in carbonate formations needs further study and discussion. Over-pressure can be identified by direct and indirect methods. Direct methods such as measured pressure data obtained from drill stem test (DST), repeat formation tester (RFT), modular dynamic test (MDT) and mud weight, and they are reliable evidences that reflect the over-pressure phenomenon in permeable reservoirs. Methodology and Approaches: Pressure coefficient, which is the ratio of the actual fluid pressure versus corresponding normal hydrostatic pressure at the same depth, has also been proposed and applied to investigate over-pressure. On the contrary, indirect methods, such as well logging, seismic and rock mechanic data, can identify abnormal pressure zones based on various response anomalies compared with the normal pressure system. The main objective of this study is to determine pore pressure using Eaton’s and Bowers’ methods and to compare their accuracy and usage. To obtain this goal in Bowers’ method, researchers try to directly link the formation velocity to the effective stress. One of these models was developed by Bowers (1995). Results and Conclusions: Sonic and density data in the distance between wells have been predicted using a combination of sequential Gaussian simulation and collocated cokriging techniques. Then, effective stress cube and overburden pressure cube have been predicted using velocity to effective stress transform and density to overburden pressure relation. Eventually, formation pore pressure has been predicted using Terzaghi’s method. Another way to estimate pore pressure is used from well logging data by applying Eaton's method (1975) with some modifications. In this way, sonic transient time trend line is separated by lithology changes determined from Zhang’s method. Our results show that the best correlation with the measured pressure data is obtained by the modified Eaton’s method with the Eaton’s exponent of about 0.4. PoreKeywords: Pore Pressure , Eaton’s Method , Bowers’ Method , Acoustic Impedance, Sequential Gaussian Simulation , Collocated Cokriging
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نشریه کواترنری ایران، پیاپی 14 (تابستان 1397)، صص 163 -177آبخوان دربرگیرنده پیت معدن گهرزمین از دو بخش آبرفتی و سنگی تشکیل شده است. لایه فوقانی از آبرفت های کواترنری و سازند سخت زیرین عمدتا از سنگ های دگرگونی مربوط به کمپلکس گل گهر ساخته شده است. در سازند سخت، به دلیل وضعیت تکتونیکی منطقه و درزها و شکاف ها و بازشدگی ها، آب های زیرزمینی به سمت پیت معدن تمرکز یافته اند. وجود این آب در پیت معدن، علاوه بر مزاحمتی که در عملیات استخراج ایجاد می کند، سبب ناپایداری دیواره های پیت و ایجاد هزینه های اضافی در عملیات انفجار می شود. بنابراین، ضروری است محل زون های تراوا با استفاده از روش های زمین آمار شناسایی شوند و در طراحی آینده سیستم زهکشی پیت معدن مدنظر قرار گیرند. در این پژوهش روش شبیه سازی زمین آماری گاوسی متوالی جهت نیل به این هدف به کار رفت. تعداد 87 گمانه اکتشافی در لایه متراکم آبرفت کواترنری و سازند سخت موجود است که داده های شاخص کیفیت مغزه حفاری (RQD) از آن ها برداشت شد. در این مطالعه تحلیل اکتشافی مکانی داده ها، شامل بررسی آمار مقدماتی و نقشه موقعیت مکانی و نمودار فراوانی و تغییرنما روی داده های متغیر RQD، انجام شد. بررسی آمار مقدماتی نشان داد این متغیر از توزیع نرمال تبعیت نمی کند. اعمال وزن دکلاسترینگ تاثیر چندانی بر توزیع آماری داده ها نداشت. بنابراین، داده ها با یک تبدیل گاوسی به مقادیر نرمال تبدیل شدند و تغییرنمای بدون جهت و جهت دار مقادیر نرمال متغیر مذکور ترسیم شد. سه جهت Azimuth 0-Dip 0، Azimuth 90- Dip 0، و Dip 90 بهترین پیوستگی مکانی را نشان دادند. این سه جهت با یک دیگر تلفیق شدند و یک مدل واحد به آن ها برازش یافت. بررسی تغییرنمای سه بعدی نشان داد بیشترین پیوستگی مکانی در جهت شرقی غربی نسبت به دو جهت دیگر وجود دارد. در نهایت شبیه سازی گاوسی متوالی متغیر RQD با استفاده از تغییرنمای سه بعدی مقادیر نرمال صورت گرفت و نقشه عدم قطعیت شبیه سازی ها رسم شد. نتایج نشان داد قسمت های جنوب شرقی، جنوب غرب، و غرب پیت بیشترین احتمال وجود زون های تراوا را دارند.کلید واژگان: تراوایی، زمین آمار، شبیه سازی گاوسی متوالی، نرم افزار ایساتیس، RQDIn this research, a sequential Gaussian simulation method has been used to determine the permeable zones in the hard-rock aquifer of the Gohr-Zamin open pit mine. For this purpose, 4946 RQD data from eighty-seven exploratory boreholes was used and exploratory-spatial data analysis of these data was performed using the preliminary statistics, location maps, histograms and variograms. Results of preliminary statistics show that this variable has not a normal distribution and that the statistical parameters are not significantly affected considering the declustering weights. The RQD data was transformed to a normal distribution with a Gaussian transform. In the next step, the omnidirectional/directional experimental variograms of RQD data were calculated and modeled using the standard models. Three directions of (1) Azimuth 0-Dip 0, (2) Azimuth 90- Dip 0 and (3) Dip 90 show the best spatial continuity. These variograms were combined together in a one single model. The highest spatial continuity is in the east-west direction compared to the other two directions. Finally, the sequential Gaussian simulation of RQD variable was performed using the 3D modeled variogram and normalized data. A probability map was generated using the results of 100 simultaions. Results show that the southeastern, southwest, and western parts of the mine pit are the best places for drilling new pumping wells.IntroductionGohar-Zamin iron ore mine is located in 50 km southwest of Sirjan city in Kerman province. Due to the tectonic condition, fracture and fissure in the hard-rock aquifer of area, the groundwater has been concentrated on the pit mine. Therefore, identifying the permeable zones is essential to mine dewatering process.Materials and methodsIn this research, ISATIS software has been used to sequential Gaussian geostatistical simulation. The exploratory-spatial data analysis was performed including preliminary statistics, location map, histogram and variograms of RQD values. Then the cell declustring method is used to decluster the RQD variable. Moreover, Gaussian transform method is applied to data normalization. In order to investigate the spatial continuity of the RQD variable, the omnidirectional and directional variograms were generated. Finally, sequential Gaussian simulation as well as simulation uncertainty analysis have been performed using three-dimensional variograms of the RQD normal values.Results and discussionIt is clear from the indicator maps that high RQD values are concentrated in the south of pit and deeper levels. It is influenced by the shape of the iron ore deposit. According to the value of skewness and kurtosis coefficients of RQD, it seems that this variable do not has the normal distribution. The 3D variogram on the XY, XZ and YZ planes indicate (a) lower spatial continuity in the north-south direction relative to the east-west direction, (b) spatial continuity in the eastern-western axis is greater than the Z axis and (c) spatial continuity in the Y direction is greater than the Z direction. The final floor level in the pit is very important for designing and determining the position of pumping wells to dewatering process. Therefore, results of 100 simulations were overplayed. The mean values of simulations calculated from the final floor level in the pit to the top of hard-rock aquifer. It was observed that at each elevation, minimum of RQD were concentrated in certain regions. These maps can be used to determine the high permeable zone.
Also, two main strike-slip faults with an almost NW-SE and E-W trend, pass through the southern part of pit. These fults and crush zones are located almost in the same direction.ConclusionAccording to the results of study, the RQD variable does not follow the standard distribution and declustering weight on the data did not have much effect on the mean value. It indicats a fairly uniform distribution of RQD data in the study area. Omindirectional and directional variograms of the RQD variable (normal values) showed that this variable has good spatial continuity. Moreover, the three-dimensional variogram of the RQD indicated that the E-W direction has the highest spatial continuity relative to the two N-S and Z directions. While, the spatial continuity in the N-S direction is more than the spatial continuity in Z direction. Results showed two straight-slip faults with NW-SE and E-W trends are located in the south of pit and These have important role in greating the crushed and permeable zones. Sequential Gaussian simulation and uncertainty maps in various parts of the pit showed that regions of southeast, southwest, and west of the pit have the highest probability is the low RQD and the high permeability.Keywords: Permeability, Geostatistics, RQD, Sequential Gaussian Simulation, ISATIS software
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